Pain Relief for OsteoArthritis Through Combined Treatment (PROACT)

Inclusion Criteria:

- Unilateral or bilateral symptomatic knee OA based on American College of Rheumatology
Clinical criteria

- Participant reports primary ethnic/race group as either African American or
non-Hispanic white

Exclusion Criteria:

- Systemic rheumatic disease/condition (e.g. rheumatoid arthritis, systemic lupus
erythematosus, fibromyalgia).

- A history of clinically significant surgery to the index knee.

- Daily use of opioids. Patients using opioids daily as both continued use and temporary
withdrawal from these medications this could affect pain perception and response to
interventions will be excluded. Other medications being used will be recorded and
controlled in statistical analyses as needed.

- Use of sodium channel blockers, calcium channel blockers and NMDA receptor
antagonists, because these medications can block tDCS effects. Other medications can
potentially influence response to tDCS (e.g. SSRIs, beta-blockers); therefore,
consistent with recent recommendations, the investigators will assess use of these
medications and include them as covariates in our statistical models.

- Uncontrolled hypertension (i.e. SBP/DBP of > 150/95), cardiovascular or peripheral
arterial disease. These exclusions are in place primarily for safety reasons, because
the cold pressor task represents a cardiovascular challenge. However, uncontrolled
hypertension can also affect pain perception, which is another reason for excluding
these individuals.

- Neurological disease (e.g. Parkinson's, multiple sclerosis, epilepsy) or evidence of
previous brain injury, including stroke and traumatic brain injury.

- Serious psychiatric disorder requiring hospitalization within the past 12 months or
characterized by active suicidal ideation.

- Current substance use disorder or history of hospitalization for treatment of
substance use disorder.

- Diminished cognitive function that would interfere with understanding of study
procedures.

- Presence of non-removable magnetic material or devices (e.g. pacemakers, aneurism
clips) or claustrophobia, which could pose a risk for injury in the MRI scanner